TECHNISCHE UNIVERSITÄT MÜNCHEN the Effect Of
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TECHNISCHE UNIVERSITÄT MÜNCHEN Lehrstuhl Entwicklungsgenetik The effect of mitochondrial dysfunction on astrocytes and radial glia like stem cells in the adult hippocampus Birgit Ebert Vollständiger Abdruck der von der Fakultät Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. E. Grill Prüfer der Dissertation: 1. Univ.-Prof. Dr. W. Wurst 2. Univ.-Prof. Dr. D. C. Lie (Friedrich-Alexander Universität Erlangen- Nürnberg) Die Dissertation wurde am 25.02.2013 bei der Technischen Universität München eingereicht und durch die Fakultät Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt am 30.04.2013 angenommen. TABLE OF CONTENT 1 TABLE OF CONTENT 1 ZUSAMMENFASSUNG .................................................................................. 4 2 SUMMARY ............................................................................................... 6 3 INTRODUCTION ......................................................................................... 8 3.1 Adult neurogenesis ............................................................................................. 8 3.2 Mitochondria .................................................................................................... 12 3.2.1 Morphology and function ................................................................................................. 12 3.2.2 Oxidative Phosphorylation ............................................................................................... 15 3.2.3 Mitochondrial transcription factor A - TFAM ................................................................... 16 3.2.4 TFAM-deficient mouse models ........................................................................................ 19 3.2.5 Mitochondria in ageing and mitochondrial diseases ....................................................... 21 3.3 Astrocytes ......................................................................................................... 24 3.3.1 Morphology and Function ................................................................................................ 24 3.3.2 Reactive gliosis and astrocytic diseases ........................................................................... 27 3.4 Aim of this study ............................................................................................... 29 4 RESULTS ................................................................................................. 30 4.1 The GLAST::CreERT2 system - a tool to target distinct brain regions ................... 30 4.2 Analyzing the effect of TFAM depletion in the hippocampal neurogenic niche ... 35 4.2.1 Reduced proliferation and survival of newborn neurons in the DG of young recombined TFAM-depleted CAG-CAT-EGFP x GLAST::CreERT2 x (TfamloxP/loxP) mice .......................... 35 4.2.2 Fate decisions are impaired in adult hippocampal stem cells in TFAM-depleted mice ... 39 4.2.3 TFAM-deficient mice maintain a glial population with radial morphology ...................... 42 4.3 Morphological analyses of TFAM-deficient newborn neurons in the adult DG .... 43 4.3.1 TFAM-depleted neural stem cells generate morphologically distinct developing neurons in GLAST::CreERT2 x Tfam-/- mice - morphology analyses ................................................ 43 4.3.2 Physical activity can increase mitochondrial content in WT newborn neurons but fails to do so in TFAM-deficient mice ........................................................................................... 49 4.3.3 TFAM deficiency does not alter spine density in adult-born neurons ............................. 53 4.3.4 TFAM depletion in neural stem cells leads to morphologically different mature neurons in running GLAST::CreERT2 x Tfam-/- mice ........................................................................ 55 4.3.5 Acute TFAM depletion by retroviral targeting of newborn neurons in the DG led to impaired morphological development in 90 days old TFAM-deficient cells, but not in 28 and 42 dpi ......................................................................................................................... 59 4.4 Up-regulation of glial fibrillary acidic protein caused by a TFAM-deficient astrocytic population ........................................................................................ 61 4.5 Behavioral phenotyping of the CAG-CAT-EGFP x GLAST::CreERT2 x (TfamloxP/loxP) mice .................................................................................................................. 65 TABLE OF CONTENT 2 4.5.1 Rotarod (RR): TFAM deficiency does not cause motor coordination defects .................. 67 4.5.2 No strong anxiety or locomotor deficiency detectable in TFAM-depleted mice in the Open Field (OF) ................................................................................................................. 69 4.5.3 Pre-Pulse Inhibition (PPI) did not reveal any striking defects in basic neuronal function 72 4.5.4 Significant impairment of Social Discrimination (SD) capability in one year old young recombined TFAM-deficient mice .................................................................................... 73 4.5.5 TFAM depletion in hippocampal adult-born neurons is not affecting hippocampal learning as needed in the Water Cross Maze (WCM) ...................................................... 75 4.5.6 TFAM-deficient mice do not exhibit a depression-like behavior in the Forced Swim Test (FST) .................................................................................................................................. 77 5 DISCUSSION ............................................................................................ 79 5.1 TFAM depletion and mitochondrial dysfunction in the GLAST::CreERT2 x TfamloxP/loxP mice ............................................................................................... 80 5.2 Mitochondrial dysfunction in adult astrocytes is linked to ageing associated phenotypes ....................................................................................................... 81 5.3 TFAM depletion in astrocytes has profound impact on adult neurogenesis ........ 83 5.4 Additional phenotypes ...................................................................................... 86 5.5 The influence of acute and chronic TFAM depletion on the morphology of newborn neurons, their spine and mitochondrial content .................................. 87 5.6 Future directions ............................................................................................... 91 6 MATERIALS AND METHODS ......................................................................... 93 6.1 Materials .......................................................................................................... 93 6.1.1 Histological solutions ........................................................................................................ 93 6.1.2 Cell culture media and solutions ...................................................................................... 94 6.1.3 Molecular biology solutions ............................................................................................. 95 6.1.4 Commercial kits (Manufacturer) ...................................................................................... 96 6.1.5 Primary antibodies ........................................................................................................... 97 6.1.6 Secondary antibodies ....................................................................................................... 97 6.1.7 Plasmids ............................................................................................................................ 97 6.1.8 Primer ............................................................................................................................... 98 6.1.9 Software ........................................................................................................................... 99 6.2 Methods .......................................................................................................... 100 6.2.1 Statistical analyses .......................................................................................................... 100 6.2.2 Mouse Analyses .............................................................................................................. 100 6.2.2.1 Breeding strategies .................................................................................................. 100 6.2.2.2 Tailclip DNA-isolation and Genotyping .................................................................... 101 6.2.2.3 Retroviral Injections and Virusproduction .............................................................. 103 6.2.2.4 Tamoxifen and BrdU injections ............................................................................... 105 6.2.2.5 Perfusion and tissue processing .............................................................................. 105 TABLE OF CONTENT 3 6.2.2.6 Immunohistochemistry ........................................................................................... 105 6.2.2.7 Morphology analyses using Imaris 7.5 .................................................................... 106 6.2.2.8 Spine analysis and mitochondrial fragmentation or elongation analysis